Ionizing radiation in the variable active galaxy 3C 120.

Abstract

The change in the C IV/Lyα line ratio when the continuum intensity changes, in the spectrum of the radio-loud active galaxy 3C 120, has been modelled. This analysis defines (i) the average parameters of the broad- line region in this galaxy and (ii) the ionizing spectrum seen by the clouds in this region. A soft extreme-ultraviolet continuum is required to model the observed trend in the line ratio.